A Distributed Computing Environment (DCE) system runs in an AIX environment on a client server mode wherein a distributed application is divided into two parts, one part residing in the user workstation and the other part residing in the server which manages data for several users. The server and the associated users constitute a DCE logical cell which is therefore a collection of machines, users and resources managed by a server. For example, the system could be an organization made up of several departments located in different buildings and operating on their own budgets. In such a case, each department could be associated with one logical cell.
A DCE cell can be configured in many ways depending on the users' requirements. Generally, a cell consists of a part of a network connecting three kinds of nodes: the DCE user workstations, the DCE administrator workstation which is provided with DCE administrator software enabling a DCE administrator to manage the DCE system services in the cell, and a server machine. The Server machine is generally equipped with special software enabling it to provide several DCE services and appears as several servers such as a Cell Directory Server (CDS) listing all the objects present in the cell, a Distributed Time Server (DTS) keeping the clocks of all the machines in the cell, and a Security Server providing the security in the cell. Other server functions may also be present in the cell such as the server function enabling the CDS of the cell to communicate with the CDS of other cells.
In order to maintain the integrity of data in the cell, backups are made periodically. These backups are necessary in case the server crashes or in case of hardware or software problems. The only way to retrieve the data is to restore a full backup (system backup) since two kinds of data must be considered, the data belonging to the users and the data belonging to the DCE system to manage users. A full backup is also required when there is a need to create a new DCE cell in order to manage supplementary users. In such a cell duplication, after installing and configuring the DCE software code on the server of the new cell, the DCE databases have to be built on this server. In both cases of backup/restore or duplication, the users cannot work during all the time taken by the operation. Therefore, such an operation cannot be made frequently in order to avoid stopping the user work, thereby resulting in the risk of losing data within the interval between two backup operations.